P. A. Veitch et al in the article “A distributed protocol for fast and robust virtual path restoration”, 1995, The Institution of Electrical Engineers; printed and published by the IEE, Savoy place, London WC2R 0BL, UK, describe (in section 2.2) a principle of organizing standard internal tables of cross-connecting devices for providing a so-called protection virtual path switching in a network. In the case of pre-assigned path restoration, the standard internal table associates a particular input port with a particular output port, wherein each of them is reserved either for a specific working path or for a specific protection path of a single data stream.
Currently optical transport networks are (semi-)permanent in the sense that provisioning of connections is done on a long term basis. Most often, services are protected in the SONET/SDH layer with static protection mechanisms. Up to now, IP networks purely rely on slow but failure robust IP rerouting mechanisms. These will be enhanced in future by MPLS (Multi Protocol Label Switching) restoration functions. Optical transport networks (OTN) today are mostly based on static WDM (wavelength de-multiplexing) system connections. However, with the introduction of fast reconfigurable optical switching nodes like Optical Add Drop Multiplexers (OADMs) and Optical Cross Connects (OXCs), the optical layer may dynamically provide optical channel services and virtual topologies to higher layers. So-called control planes are defined in specific standardization documents and forums (for example, http://www.oiforum.com). A control plane, contrary to a data plane, mainly consists of distributed routing and signaling functions needed for connection control. With the availability of a control plane for the optical layer, MPLS-like restoration mechanisms based on optical channels can be introduced in OTNs. The Generalized Multiprotocol Label Switching (GMPLS) framework extends the Multiprotocol Label Switching (MPLS) concept for other layers than the IP layer, such as TDM layer or the optical layer. The creation and routing of Label Switched Paths (LSPs) can be done statically by the network management or dynamically through routing and signaling protocols. It is possible to port the control plane principle of MPLS, with modifications, to other layers like the optical layer. (For example, M. Jaeger et al, “Evaluation of Novel Resilience Schemes in Dynamic Optical Transport Networks”—work within the TransiNet project, supported by the Federal German Ministry of Education and Research, 2003).
It should be noted, however, that restoration techniques based on the use of the above-mentioned signaling protocols are complex and, the associated recovery time is often too long in comparison with optical transport network requirements, especially for services such as voice.
To the best of the Applicant's knowledge, there are no prior art solutions which would enable quick switching (reconfiguring) in mesh networks supporting SDH/SONET traffic in cases where shared protection paths are utilized without relying on the invocation of distributed routing and signaling as described in the above.